1. Field of the Invention
The present invention relates to a method of forming a display panel and, more particularly, to a method of forming a display panel that uses twisted molecules of the photoelectric twisting layer to induce surface molecules of the alignment material to arrange in an ordered state, and the alignment material is polymerized according to the ordered state to form an alignment film
2. Description of the Prior Art
Liquid crystal display (LCD) can control brightness or hue of its displaying pixels by twisting the liquid crystal molecules. That is because the liquid crystal molecules with different twisting angles allow different light-penetrations for various colorful images. Usually, alignment films are included in the LCD to pre-tilt the nearby liquid crystal molecules, so the twisting direction of the liquid crystal molecules can be well controlled in the pixels. For forming the alignment films, a traditional aligning method called a rubbing alignment treatment is adopted in common.
The rubbing alignment treatment includes a step of coating the thin film transistor (TFT) substrate and the color filter (CF) substrate respectively with alignment material before the TFT substrate and the CF substrate are combined with each other, and a step of rubbing the alignment material, which covers the TFT substrate and the CF substrate, with a roller having nap (fluff). In other words, the rubbing alignment treatment is performed on semi-finished substrates (half-finished substrates or unfinished substrates), such as the semi-finished TFT substrate and the semi-finished CF substrate, which are not assembled. Nevertheless, the rubbing alignment has shortcomings of falling dusts from the roller, causing abnormal stress, probably forming some un-uniform alignment, and so on. Thus, non-contact type alignment treatments, such as a photo alignment treatment, an ion beam alignment treatment and a plasma beam alignment treatment, are aggressively developed. However, the above-mentioned non-contact type alignment treatments are still carried out on the semi-finished substrates (half-finished substrates or unfinished substrates) before the TFT substrate and the CF substrate are combined with each other. The fabricating method including a non-contact type alignment treatment is described in detail as following.
Referring to FIG. 1 through FIG. 4 schematically illustrate a method of forming a multi-domain vertical alignment (MVA) liquid crystal display panel by utilizing a prior art photo alignment treatment, where FIG. 2 is a cross-sectional diagram of the glass substrate shown in FIG. 1. As shown in FIG. 1 and FIG. 2, a glass substrate 12 and a conductive layer 14 disposed on the inner surface of the glass substrate 12 are first provided. A plurality of pixel regions 16 are defined on the glass substrate 12. For clarity, only one pixel region 16 is shown in FIG. 1 and FIG. 2, and some components are not marked in both FIG. 1 and FIG. 2. The glass substrate 12 is a semi-finished substrate (half-finished substrate or unfinished substrate), and a first alignment region 18a, a second alignment region 18b, a third alignment region 18c and a fourth alignment region 18d can be further defined in each pixel region 16.
Thereafter, the glass substrate 12 is coated with an alignment material 20, which is radiation-polymerizable and has molecules arranging in a non-aligned state (non-ordered state). In order to form an alignment film having different pre-tilt angles in the first, second, third and fourth alignment regions 18a, 18b, 18c, 18d, four exposing processes have been performed on the alignment material 20 disposed in the first, second, third and fourth alignment regions 18a, 18b, 18c, 18d respectively. As shown in FIG. 1 and FIG. 2, a first exposing step is performed, where the second, third and fourth alignment regions 18b, 18c, 18d are shielded by a mask 22, and the first alignment region 18a is exposed by the mask 22. Wherein the mask 22 has a shield material (unshown) and is disposed on the transparent substrate (unshown) to define transmission region (unshown) and shielding region (unshown) in one pixel, the transmission region is corresponding to predetermined region (such as the first alignment region 18a) radiated by polarized light or parallel light 24, and the shielding region is corresponding to other regions (such as the second, third and fourth alignment regions 18b, 18c, 18d), and the mask 24 is not in contact with the alignment material 20. The alignment material 20 disposed in the first alignment region 18a is radiated by polarized light or parallel light 24 that has an tilt angle of 45 degree (45°) to the glass substrate 12.
As shown in FIG. 3, the second, third and fourth exposing steps are performed one after another to radiate the alignment material 20 disposed in the second, third and fourth alignment region 18b, 18c, 18d with polarized light or parallel light 24 that has an tilt angle of 135°, 225° and 315° to the glass substrate 12 respectively. As shown in FIG. 4, the parallel light or polarized light 24 having a particular direction induces superficial molecule of the alignment material 20 orient along a predetermined direction, and the parallel light or polarized light 24 can polymerize the alignment material 20 in the meantime to turn the alignment material 20 into an alignment film 26. Therefore, the alignment film 26 has different pre-tilt directions 28 in the first, second, third and fourth alignment regions 18a, 18b, 18c, and 18d respectively.
Although the photo alignment treatment reduces the shortcomings of dusts from the roller, abnormal stress and un-uniform alignment, the photo alignment treatment still has a disadvantage of expensive equipment cost. For providing the parallel light or polarized light 24, exquisite lens system in the photo alignment equipment is needed. Accordingly, if a larger area (larger size substrate such as 800 mm*500 mm) should be exposed in an exposing process, an exquisite lens system having a great aperture is required in the photo alignment equipment. However, an exquisite lens system having a great aperture usually takes a lot of expenses.
Furthermore, a plurality of exposing steps are needed to form one alignment film of a multi-domain alignment structure for various pre-tilt angles in one semi-finished substrate (half-finished substrate or unfinished substrate). The numerous exposing steps not only increase the cycle time and complexity of manufacturing the product, but also needs additional cost for the photo masks. In addition, the product structure and the product design are great limited by the precision of radiating the light, the precision of orient the exposing target, the precision of aligning the photo mask, and so on, due to the numerous exposing steps.
Moreover, the photo alignment treatment is still carried out on the alignment material covering the semi-finished substrates (half-finished substrates or unfinished substrates) before the TFT substrate and the CF substrate are assembled. Therefore, although the falling dusts from the roller is avoided, the photo alignment treatment still has a shortcoming of falling dusts from surrounding, and the dusts may cause problems, such as bright dots, dark dots, etc.